1. Field of the Invention
The present invention relates to an apparatus for manufacturing a slide fastener stringer including a woven stringer tape and a coiled coupling element woven into the stringer tape along a longitudinal edge thereof.
2. Prior Art
Known apparatus for producing a slide fastener stringer of the type described above generally comprise a shuttleless loom such as a needle loom for weaving a stringer tape and a rotor assembly operatively associated with the loom for supplying a monofilament and a core thread, the rotor assembly including a mandrel for extending along a longitudinal edge of the tape being formed, and adjacent to the fell of the tape. The rotor assembly winds or coils the monofilament around the mandrel and the core thread fed therealong, thereby forming the coiled coupling element reinforced with the core thread as they are woven into the tape by being interlaced with weft threads inserted by filling carriers of the loom.
The rotor assembly comprises a housing, a wheel or rotor rotatable in the housing and having an axial off-center hole through which the monofilament passes, and a hollow axle around which the wheel is rotatable and thorugh which the core thread is supplied from a bobbin on the axle, the mandrel being fixed to the axle. Since during operation of the apparatus the wheel revolves so as to turn the monofilament in an orbital motion around the axle, the axle floats in the wheel and is held nonrotatable only by the mandrel that engages the coiled coupling element wound therearound and woven into the stringer tape. Therefore, the axle is liable to get jiggled and turned about its own axis due primarily to frictional engagement with the revolving wheel and to vibrations transmitted from the mandrel around which monofilament coiling action takes place. Such movements of the axle in turn amplify vibratory movements of the mandrel, which grow greater and greater as the wheel rotates at higher speeds. This condition has led to drawbacks in that the monofilament being coiled can be shaped irregularly and the weft threads being inserted tend to get loosened at the tape edge. Furthermore, the filling carriers which reciprocate across the mandrel to insert the weft threads may collide with the vibrating mandrel, whereby the mandrel can be bent or broken.
To solve such problems, there has been devised an apparatus for manufacturing a woven slide fastener stringer, as disclosed in U.S. Pat. No. 4,174,736, filed on Nov. 3, 1978, assigned to the present assignee, the apparatus having a mandrel that is held stationarily at all times with respect to the frame of the apparatus.
One problem with the conventional apparatus is that since the mandrel extends obliquely with respect to the warp threads for the stringer tape, the monofilament is subjected to varying tension as it moves toward and away from the warp threads while revolving around the mandrel. The monoflament under fluctuating tension tends to be wound into irregular coils with enlarged coupling heads displaced out of position, resulting in poor quality and malfunctioning of slide fasteners.
When a relatively large bobbin of core thread is to be used, the rotor assembly has to be located away from the warp threads so that the bobbin will not interfere with the warp threads. With such an arrangement, however, the monofilament as it moves around the mandrel forms a larger angle with respect to the warp threads than it would otherwise do with the results that the monofilament will be supplied under more varying tension and the legs of formed coupling elements will be inclined with respect to the warp threads.